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Topic:Genetics
Genetics in horses encompasses the study of hereditary traits and the genetic makeup that influences various characteristics and health conditions in equine populations. This field involves the analysis of genes and their functions, inheritance patterns, and the impact of genetic variations on traits such as coat color, performance ability, and susceptibility to diseases. Research in equine genetics employs techniques such as genome mapping, sequencing, and genetic testing to identify specific genes and mutations associated with these traits. This page gathers peer-reviewed research studies and scholarly articles that explore the genetic basis of equine traits, the methodologies used in genetic research, and the implications for breeding, health management, and conservation of horse breeds.
Hyperkalaemic periodic paralysis in Australian quarter horses. Three Quarter Horse stallions and 5 of their 11 tested progeny were diagnosed as affected with the inherited autosomal dominant defect hyperkalaemic periodic paralysis in Victoria in 1992. The diagnoses were based on the appearance of clinical signs and associated increased plasma potassium concentrations in response to oral potassium loading. All affected horses were descendants of the American Quarter Horse Impressive. Indirect evidence indicates that at least 3 other affected Quarter Horse stallions have stood or are standing at stud in Australia. The clinical details of the affected horses...
Monoclonal antibodies specific for equine IgG sub-isotypes including an antibody which recognizes B lymphocytes. Equine immunoglobulin G is currently classified as consisting of five sub-isotypes: IgGa, b, and c, IgG(T), and IgG(B). The study of the role of these immunoglobulins in antigen-specific responses, and the examination of their functional properties would be greatly facilitated by the availability of monoclonal antibodies (Mabs) that distinguish between them. The production and characterization of two Mabs that recognize an IgG sub-isotype with the characteristics of IgG(ab) is described. The immunoglobulin identified by these Mabs had a heavy chain weight of 53 kDa, was of rapid cathodal elect...
Cloning and analysis of the cDNA encoding the horse and donkey luteinizing hormone beta-subunits. The coding regions of the horse (Equus caballus) and donkey (E. asinus) luteinizing hormone (LH) beta-subunit transcripts were cloned from pituitary gland RNA, in order to investigate their relationships to the corresponding equine chorionic gonadotropin (CG) beta-subunits and to further understand the unusual receptor-binding properties of equine LH and CG. The horse and donkey LH beta-subunit sequences were very similar (97% identity at the nucleotide (nt) level; 93% at the amino acid (aa) level), confirming their very close evolutionary linkage and also indicating that the C-terminal extens...
Incorporation of uracil into viral DNA correlates with reduced replication of EIAV in macrophages. The retrovirus equine infectious anemia virus (EIAV) encodes a dUTPase situated between reverse transcriptase and integrase. We have described the inability of EIAV with a 270-bp dUTPase deletion, delta DU EIAV, to replicate to wild-type (WT) levels in equine macrophages (D. S. Threadgill, W. K. Steagall, M. T. Flaherty, F. J. Fuller, S. T. Perry, K. E. Rushlow, S. F. J. LeGrice, and S. L. Payne, J. Virol. 67, 2592-2600, 1993). Here we describe the construction of a second dUTPase-deficient virus (DUD71E) containing a single amino acid substitution in dUTPase. delta DU and DUD71E replicate to ...
Monoclonal equine IgM and IgG immunoglobulins. In order to define equine immunoglobulins (Igs) and to produce monoclonal reference Igs we fused equine peripheral blood mononuclear cells with X63-Ag8.653 non Ig producing murine myeloma cells. A total of 29 equine Ig producing equi-murine heterohybridomas were obtained, of which ten expressed equine Ig for more than 3 months. One of these heterohybridoma lines produced monoclonal IgM, an equine isotype which has not been available in monoclonal form before. Four lines secreted equine IgG of two distinct Ig heavy chain types as assessed by the molecular weight (MW), while the remaining five l...
Complete primary sequence of equine cartilage link protein deduced from complementary DNA. Investigation of the structure of the equine articular cartilage link protein (LP) from individuals ranging in age from 1 to 15 years identified 3 distinct isoforms having molecular weights of 46,000, 43,000 and 41,000. The relative amounts of each of the 3 isoforms altered with age. The largest form did not change with age; however, amounts of the Mr 43,000 and 41,000 forms increased with increasing age. The results suggested that an accumulation, in the extracellular matrix of cartilage, of these 2 smaller products may have arisen from proteolytic cleavage. The complete amino acid sequence o...
XX male pseudohermaphroditism in a horse. A pseudohermaphrodite horse with aggressive stallion-like behavior and ambiguous external genitalia was gonadectomized. The hypoplastic gonads removed from the abdomen were confirmed by histologic examination to be testes. Examination of blood and fibroblasts revealed a 64,XX karyotype.
Volume changes of the molten globule transitions of horse heart ferricytochrome c: a thermodynamic cycle. Volume changes among the unfolded (U), native (N), and molten globule (MG) conformations of horse heart ferricytochrome c have been measured. U to N (pH 2 to pH 7) was determined in the absence of added salt to be -136 +/- 5 mL/mol protein. U to MG (pH 2, no added salt to pH 2, 0.5 M KCl) yielded + 100 +/- 6 mL/mol. MG to N was broken into two steps, N to NClx at pH 7 by addition of buffered KCl to buffered protein lacking added salt (NClx = N interacting with an unknown number, X, of chloride ions), and MG to NClx by jumping MG at pH 2 in 0.5 M KCl to pH7 at the same salt concentration. The d...
In vitro and in vivo evidence on the site of neutralization of equine chorionic gonadotrophin (eCG) by an eCG antiserum. This study was designed to determine whether the major site of eCG neutralization by an antiserum to the hormone is at the peripheral or ovarian level. Hamsters hypophysectomized at oestrus were injected s.c. with 25 iu eCG. Three days later, preovulatory follicles were dissected and cultured for 5 h and the medium was changed every hour. At the end of the first hour of incubation, oestradiol and androstenedione accumulation was high, with a sharp drop over the next 4 h, whereas progesterone concentrations did not change over the entire period. Addition of eCG antiserum to the incubated follic...
A mouse model for testing the pathogenicity of equine herpes virus-1 strains. A mouse model was developed for testing the pathogenicity of equine herpes virus-1 (EHV-1) strains. The model was validated with EHV-1 strains that are known to be of a low or high pathogenicity in horses. From all parameters tested, the safety index, which was calculated from the body weights of the mice after infection, proved to be the best predictive parameter. When this parameter was used, good and reliable correlations were found with the pathogenicity of the EHV-1 strains in horses. This method enabled the differentiation between the two experimental EHV-1 strains whose genetic backgrou...
The DNA sequence of equine herpesvirus 2. The complete DNA sequence of equine herpesvirus 2 (EHV-2) strain 86/67 was determined. The genome is 184,427 bp in size and has a base composition of 57.5% G + C. Unusually for a herpesvirus, about a third of the sequence distributed in several large blocks appears not to encode proteins. The 79 open reading frames that were identified as probably polypeptide-coding are predicted to encode 77 distinct proteins. Amino acid sequence comparisons confirmed that EHV-2 is a gamma-herpesvirus that is genetically collinear with herpesvirus saimiri (HVS; a gamma 2-herpesvirus) and Epstein-Barr virus (E...
Partial complementary deoxyribonucleic acid cloning of equine relaxin messenger ribonucleic acid, and its localization within the equine placenta. To determine the site of relaxin gene expression in equine placentae, a set of degenerate oligonucleotide primers was made according to the published amino acid sequence of the A- and B-chain of equine relaxin (eRXN). Total cellular RNA (tcRNA) from equine placentae at about 120 and 300 days of pregnancy was subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) with use of these primers. A single amplification product of approximately 430 bp was detected in each case by agarose gel electrophoresis. The PCR product was ligated into Bluescript plasmid and sequenced to confirm the...
Effect of enzymes on the growth of human and animal rotaviruses. The growth of group A human, bovine, equine and porcine rotaviruses were enhanced by pretreatment of virus with pancreatin, trypsin, protease, alkaline phosphatase or pepsin and incorporation of these enzymes in maintenance medium. In contrast, alpha-amylase or lipase inhibited the growth of equine and porcine rotaviruses. The other enzymes, adenosine deaminase, lactase, lysozyme, ribonuclease or triose-phosphate isomerase gave little or no change in the growth of all four rotaviruses.
Comparative ribotyping of Staphylococcus intermedius from dogs, pigeons, horses and mink. Strains of Staphylococcus (S.) intermedius from dogs, pigeons, horses and mink were typed by comparison of rRNA gene restriction fragment length polymorphisms (ribotyping) and the resulting ribotypes examined by cluster-analysis. Digestion of whole-cell DNA with HindIII resulted in 9 ribotypes with 3 to 4 bands. Separation of isolates from different host animal species was not possible. EcoRI yielded 11 different patterns with 4 to 9 fragments. The EcoRI-ribotypes of all canine strains grouped in one cluster encompassing four closely related ribotypes. Isolates were indistinguishable with resp...
At least four MHC class I genes are transcribed in the horse: phylogenetic analysis suggests an unusual evolutionary history for the MHC in this species. Nineteen horse MHC class I specificities have been serologically identified previously at a single locus (ELA-A), and two other specificities appear to be coded at other loci. Biochemical studies indicate that there are at least two expressed loci. In order to establish the number of transcribed horse MHC class I genes, we made a cDNA library from a heterozygous animal (ELA-A3/A7), and screened for positive clones using a bovine class I probe. More than 200 class I clones were isolated in this way, and so far seven unique full length sequences have been identified. All of the sequences are pre...
Extensive mtDNA diversity in horses revealed by PCR-SSCP analysis. The hypervariable D-loop region of mitochondrial DNA (mtDNA) was amplified with the polymerase chain reaction using total horse DNA samples. Analysis of single strand conformation polymorphism (SSCP) of denatured amplification products was carried out by native polyacrylamide (8%) gel electrophoresis followed by silver staining. As many as 15 distinct SSCP variants were revealed when screening a total of 78 maternally unrelated horses representing five different breeds. All breeds showed a high degree of polymorphism and the estimated probability (PImt) that two maternally unrelated individual...
Molecular cloning of cDNA for equine ovarian inhibin/activin beta A subunit. cDNAs encoding equine inhibin/activin beta A subunit were isolated from an equine follicle cDNA library and characterized. Using primers based on the rat inhibin/activin beta A subunit cDNA sequence, a RT-PCR was performed to generate the probe for screening. Four positive clones were isolated. Analysis of the nucleotide sequence of these clones revealed that two pairs of identical clones were present, Eq-beta A-1 (0.9 kb) and Eq-beta A-2 (1.5 kb). Eq-beta A-2 clone contained a complete open reading frame encoding 426 amino acids. The deduced amino acid sequence of equine inhibin/activin beta ...
Comparative RAPD-PCR analysis of lungworms (Dictyocaulidae) from fallow deer, cattle, sheep, and horses. Genomic DNA isolated from the four Dictyocaulus species D. viviparus, D. eckerti, D. filaria and D. arnfieldi was compared by random amplified polymorphic DNA polymerase chain reaction (RAPD)-PCR to get additional information whether lungworms from fallow deer belong to a separate species (D. eckerti) or have to be regarded as an isolate of D. viviparus in wild ruminants. The resulting banding patterns of the electrophoresed PCR products were compared to assess the degree of genetic differences between the different lungworms. For the two D. viviparus isolates a similarity coefficient of 93.4%...
Sodium channel inactivation is impaired in equine hyperkalemic periodic paralysis. 1. Equine hyperkalemic periodic paralysis (E-HPP) is a dominantly inherited disorder of muscle that causes recurrent episodes of stiffness (myotonia) and weakness in association with elevated serum K+. Affected horses carry a mutant allele of the skeletal muscle isoform of the Na channel alpha-subunit. To understand how this mutation may cause the disease phenotype, the functional defect in Na channel behavior was defined physiologically by recording unitary currents from cell-attached patches on normal and affected equine myotubes. 2. The presence of the mutation was confirmed in our cell lin...
Application of the polymerase chain reaction to the detection of African horse sickness viruses. The development of a coupled reverse transcriptase-polymerase chain reaction assay (RT-PCR) is described for the detection of African horse sickness virus (AHSV) double-stranded RNA. Genome segments 7 and 10 were chosen as target templates for primers selected for use in the RT-PCR. Using these AHSV-specific primers all 9 serotypes were detectable. The sensitivity and specificity of the RT-PCR results were compared to those obtained by competition ELISA.
Regulatory function of the equine herpesvirus 1 ICP27 gene product. The UL3 protein of equine herpesvirus 1 (EHV-1) KyA strain is a homolog of the ICP27 alpha regulatory protein of herpes simplex virus type 1 (HSV-1) and the ORF 4 protein of varicella-zoster virus. To characterize the regulatory function of the UL3 gene product, a UL3 gene expression vector (pSVUL3) and a vector expressing a truncated version of the UL3 gene (pSVUL3P) were generated. These effector plasmids, in combination with an EHV-1 immediate-early (IE) gene expression vector (pSVIE) and chimeric EHV-1 promoter-chloramphenicol acetyltransferase (CAT) reporter constructs, were used in trans...
Interaction of beta-lactoglobulin with retinol and fatty acids and its role as a possible biological function for this protein: a review. beta-Lactoglobulin is the major whey protein in the milk of ruminants and some nonruminants, such as pigs and horses. Although beta-lactoglobulin was first isolated 60 yr ago, no function has been definitely ascribed to beta-lactoglobulin. Recent x-ray crystallographic studies have advanced knowledge of the structure of beta-lactoglobulin, which is homologous with that of retinol-binding protein and lipocalycins; the function of these proteins seems to be participation in the transport of small hydrophobic substances. By analogy, this protein has been suggested as having a role as a transporte...
Substitutions of isoleucine residues at the adenine binding site activate horse liver alcohol dehydrogenase. The contributions of isoleucine residues 224 and 269 of horse liver alcohol dehydrogenase to binding of the adenine moiety of NAD and to catalysis were studied by replacing Ile-224 with glycine (I224G) and Ile-269 with serine (I269S). The kinetic mechanisms of wild-type and both mutated liver enzymes were ordered. Affinities for several adenosine derivatives were decreased 5-50-fold by both substitutions. The I269S mutation differentially destabilized binding of the complete coenzyme, as affinities for NAD+ and NADH were decreased about 60-fold with the I224G enzyme and 350-fold for the I269S ...
A morbillivirus that caused fatal disease in horses and humans. A morbillivirus has been isolated and added to an increasing list of emerging viral diseases. This virus caused an outbreak of fatal respiratory disease in horses and humans. Genetic analyses show it to be only distantly related to the classic morbilliviruses rinderpest, measles, and canine distemper. When seen by electron microscopy, viruses had 10- and 18-nanometer surface projections that gave them a "double-fringed" appearance. The virus induced syncytia that developed in the endothelium of blood vessels, particularly the lungs.
